The invention relates to internal combustion engines, and more specifically, to an improved air supply arrangement for such engines. According to the invention, a by-pass line is provided which by-passes the load-regulating member or throttle valve in the main air supply line. For example, the arrangement of the invention could be used with an internal combustion engine of the type with an air measuring, independent drive fuel injection installation being supplied continuously with fuel.
Internal combustion engines with the above-noted type of injection installation are known (Bosch, Technical Instruction Gasoline Injection K-Jetronic, 1st issue February, 1974) in which, during the warm-operation phase of the engine, a larger quantity of fuel-air mixture is supplied and corresponds to the position of the load-regulating member, in order to compensate for the increased friction work of the internal combustion engine during such phase of operation. This is attained through a supplementary air slide-valve, by-passing the load-regulating member. The cross section of the supplementary air slide valve by an apertured partition controlled in dependence of the heating of an electrically heated bi-metal strip, which, during a warm operating condition of the internal combustion engine, is closed. However, this arrangement exhibits disadvantages with respect to engine starting conditions, since the additional quantity of fuel and air mixture provided during the warm-operating phase after the starting process is not always sufficiently large during the starting process, whereby, among other things, a positive start and a rapid acceleration of the internal combustion of the idling speed (no load speed) is not assured.
The present invention contemplates providing apparatus which overcomes the above-mentioned disadvantages and which optimizes the starting and warm-operation phases of an internal combustion engine of the kind mentioned above.
More specifically, the present invention contemplates the provision of a by-pass line with a supplementary air control valve controlled in dependence on the engine suction pipe vacuum. According to one preferred embodiment of the invention, a supplementary air valve is provided which has a valve disk connected with a membrane moveable therewith to open and close the by-pass line. The pressure in the main air supply line or suction pipe upstream of the throttle valve acts on one side of the membrane and, via a control line, the suction pipe pressure downstream of the throttle valve acts at the other side of the membrane. A compression spring is arranged at the site of the membrane acted upon by the suction pipe vacuum.
A further preferred embodiment of the invention includes a supplementary air valve in a housing. A valve disk, combined with a membrane, is arranged in the housing for opening and closing the by-pass line. Atmospheric pressure acts, by means of an opening in the housing, on one side of the membrane facing away from the valve disk. The suction pipe vacuum pressure downstream of the throttle valve acts on the other side of the membrane. Between the housing and the valve disk a compression spring is arranged. A separation sheet metal is arranged between the membrane and the valve disk in the housing, and this separation is provided with a throttle opening for influencing the opening and closing velocity of the valve disk in an advantageous manner.
The constructions of the present invention exhibit advantages, especially, during the start of the internal combustion engine and the rapid acceleration to the no load rotative speed, during which phases the exhaust emission of the internal combustion engine is diminished. In addition, the operation of the driver pedal during the starting process with the use of the supplementary air valve in accordance with the present invention is unnecessary. Also, by means of the supplementary air valve of the invention during start of driving, stalling of the internal combustion engine is effectively avoided since, with a too small operation of the driver pedal, the suction pipe vacuum immediately becomes so small that, by means of the supplementary air valve, the quantity of fuel-air mixture supplied to the internal combustion engine is immediately increased.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.